Cosmic-Ray Acceleration at the Forward Shock in Tycho’s Supernova Remnant: Evidence from Chandra X-Ray Observations
Cosmic-Ray Acceleration at the Forward Shock in Tycho’s Supernova Remnant: Evidence from Chandra X-Ray Observations
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DOI：
10.1086/496941
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发表时间：
2005-07
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通讯作者：
Jessica S. Warren;J. Hughes;C. Badenes;P. Ghavamian;C. McKee;D. Moffett;P. Plucinsky;C. Rakowski;E. Reynoso;P. Slane
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作者：
Jessica S. Warren;J. Hughes;C. Badenes;P. Ghavamian;C. McKee;D. Moffett;P. Plucinsky;C. Rakowski;E. Reynoso;P. Slane
我们从三个X射线观测数据中提出了在第谷超新星遗迹（SNR）的前向激波处宇宙射线加速的证据：（1）接触不连续性与前向激波或冲击波的接近程度，（2）第谷边缘发射的形态，以及（3）边缘发射的光谱性质。我们确定的位置的冲击波（BW），接触不连续性（CD），和反向冲击波（RS）周围的第谷的超新星遗迹的边缘，使用主成分分析和其他方法适用于新的钱德拉数据。BW的方位角平均半径为251“。对于CD和RS，我们发现平均半径分别为241“和183”。考虑到投影效应，我们发现比值为1：0.93：0.70（BW：CD：RS）。我们发现这些值与SNR演化的绝热流体动力学模型不一致。CD：BW比可以解释，如果宇宙射线加速的离子发生在向前冲击。RS：BW的比值，以及来自第谷喷出物的强烈Fe Kα辐射，暗示RS并没有加速宇宙射线。我们还提取径向轮廓的约34%的边缘的第谷和比较它们的模型的表面亮度轮廓背后的BW的一个纯粹的热等离子体与绝热冲击。观察到的边缘形态比模型预测的更强烈，表明这种热发射在这里是不可信的。光谱分析也暗示边缘辐射本质上是非热的，这进一步支持了第谷的前向激波加速宇宙射线的观点。
We present evidence for cosmic-ray acceleration at the forward shock in Tycho's supernova remnant (SNR) from three X-ray observables: (1) the proximity of the contact discontinuity to the forward shock, or blast wave, (2) the morphology of the emission from the rim of Tycho, and (3) the spectral nature of the rim emission. We determine the locations of the blast wave (BW), contact discontinuity (CD), and reverse shock (RS) around the rim of Tycho's supernova remnant using a principal component analysis and other methods applied to new Chandra data. The azimuthal-angle-averaged radius of the BW is 251''. For the CD and RS we find average radii of 241'' and 183'', respectively. Taking account of projection effects, we find ratios of 1 : 0.93 : 0.70 (BW : CD : RS). We show these values to be inconsistent with adiabatic hydrodynamic models of SNR evolution. The CD : BW ratio can be explained if cosmic-ray acceleration of ions is occurring at the forward shock. The RS : BW ratio, as well as the strong Fe Kα emission from the Tycho ejecta, imply that the RS is not accelerating cosmic rays. We also extract radial profiles from ~34% of the rim of Tycho and compare them to models of surface brightness profiles behind the BW for a purely thermal plasma with an adiabatic shock. The observed morphology of the rim is much more strongly peaked than predicted by the model, indicating that such thermal emission is implausible here. Spectral analysis also implies that the rim emission is nonthermal in nature, lending further support to the idea that Tycho's forward shock is accelerating cosmic rays.